FR2882664A1 - Fluidized bed reactor for liquids/solids reactions has finishing compartment with ultrasound emitters at upper end of reactor body - Google Patents

Abstract

A fluidized bed reactor, comprising a vertical body (1) with an injector (3) for a solution to be treated at its lower end, an input system (5) for a metal reagent, a solution agitator and an upper outlet (4), has a finishing compartment (6) with divergent walls at the upper end of the reactor body containing ultrasound emitters (7) that are immersed in the solution. The reactor body is cylindrical in shape and is subdivided into a number of parallel vertical compartments (11) by cylindrical or flat walls, while the injector is connected to a chamber (2) containing balls (12) of an inert material such as aluminium, plastic or glass.

Description

Device for implementing liquid / solid reactions in a fluidized bed

Technical field of the invention

  The invention relates to a device for implementing liquid / solid reactions in a fluidized bed comprising a vertical reactor body, means for injecting a solution to be treated at the lower end of the reactor, means for introducing the a reactive metal in the reactor, discharge means at the top of the reactor and stirring means of the solution.

  STATE OF THE ART In many applications, reactors use fluidized beds for carrying out physical and / or chemical reactions in a fluid medium.

  International Patent Application WO 00/47318 and European Patent Application No. 14109 describe devices for carrying out liquid / solid reactions in fluidized beds, in particular for cementation reactions, whose efficiency is improved by magnetic activation.

  OBJECT OF THE INVENTION The object of the invention is to improve the known devices.

  According to the invention, this object is achieved by the fact that the device comprises, at the upper end of the reactor body, a flared finishing compartment in which ultrasonic emitting elements are immersed in the solution.

Brief description of the drawings

  Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given by way of nonlimiting examples and represented in the accompanying drawings, in which: FIG. 1 schematically illustrates a device according to the invention.

  FIG. 2 represents a particular embodiment of an ultrasound transmitter element of a device according to FIG. 1.

  Figures 3 and 4 show, in section according to A-A, two embodiments of the reactor body of a device according to Figure 1, respectively rectangular section and circular.

  Figures 5 and 6 show a device according to Figure 1, supplemented by a stirring device, respectively ultrasonic (fig.5) and electromagnetic (fig.6).

  FIG. 7 represents, in section, a support block of the electromagnets of the stirring device according to FIG. 6.

  Description of particular embodiments

  As represented in FIG. 1, the device conventionally comprises a reactor body 1, vertical and of great height, constituting the intermediate part of the reactor and a lower part constituting an injection chamber 2. This is connected to a conduit of supply 3, provided with a non-return valve and intended for the injection of the solution to be treated into the reactor, so as to cause a vertical upward flow of the solution, forming a fluidized bed, between the feed pipe 3 and a discharge pipe 4. A loading hopper 5 makes it possible to introduce, at the upper end of the reactor, a reactive metal, for example iron shot. The mixture of the solution and the reactive metal is stirred in the reactor body 1 by appropriate stirring means, not shown in FIG.

  According to the invention, the device further comprises a flared upper portion constituting a finishing compartment 6. It thus forms in the upper part of the reactor a fluidized bed of variable section. Ultrasonic or sonotrode emitting elements 7 are immersed in the solution inside the finishing compartment 6, preferably in its upper, widest part. The section of the finishing compartment is, in its widest part, preferably equal to at least twice the section of the reactor body 1.

  The flaring of the reactor in the finishing compartment 6 causes a significant reduction in the linear velocity of the solution in this part of the reactor. By way of example, it is possible to reduce the solution speed by at least 30% in the finishing compartment with respect to the speed in the reactor body. The decrease in the relative velocity between the reactive metal particles and the solution, which is then close to zero, increases the duration of the interaction between the reactive metal and the solution and, consequently, the transfer coefficient of the reaction exchanges between the reactive metal particles and the solution.

  The ultrasonic or sonotrode emitting elements 7 immersed in the finishing compartment activate the chemical reactions at the liquid / solid interface between the solution and the reactive metal balls in this finishing compartment. They improve the kinetics of the chemical reaction and make it possible to detach the noble material formed by this reaction, which could remain stuck on the reactive metal balls. The sonotrodes 7 may, for example, be mounted on a mounting frame (not shown) secured to the walls of the finishing compartment, below the discharge duct 4. FIG. 2 illustrates a known embodiment of FIG. a sonotrode 7, comprising a piezoelectric body 8 integral with a projecting rod 9, on which are arranged one or more heads 10 (six for example), which constitute the vibrating / resonant active elements.

  At the outlet of the finishing compartment 6, the porosity, that is to say the ratio between the volume of the solution and the total volume (solution and reactive metal particles) may be greater than 0.9. Thus, at equal flow rate, the reactive metal particles, for example the iron particles, entrained out of the fluidized bed, towards the evacuation pipe 4 stay longer in the reactor and the reaction continues in the finishing compartment 6 The reactive metal particles discharged are therefore much smaller than in the known devices. This decrease increases the liquid / solid contact surface and also improves the kinetics of the reaction. The solution is thus less concentrated in noble metal at the outlet of the reactor. The proportion of reactive metal used is therefore greater and it is thus possible to save money on the quantity of reactive metal introduced into the reactor by the loading hopper 5. For the same flow rate and the same diameter of the reactive metal beads, the output of the loading hopper 5, the reactive metal gain can be of the order of 90%. The improvement of the kinetics of the reaction may possibly make it possible to reduce the total height of the reactor and above all allows an improvement in the productivity of the systems used.

  Moreover, especially in the case of carburizing, this reduces the risk of contamination of the noble metal extracted from the solution. The dimensions of the finishing compartment are chosen according to the size of the reactive metal balls introduced at the upper end of the reactor and the flow rate of the solution during its injection at the lower end of the reactor.

  As shown in FIGS. 1, 2 and 3, the reactor body 1 constituting the intermediate portion of the reactor, of uniform section, is preferably subdivided into a plurality of compartments 11, vertical and parallel to each other. A series of juxtaposed, parallel fluidized beds is thus formed. FIGS. 3 and 4 respectively show, in section along AA, a reactor body 1 of rectangular section, subdivided into compartments 11a by flat vertical walls, and a cylindrical reactor body 1, subdivided into compartments 11b in the form of concentric annular cylinders.

  The reactor body 1 and its partition walls of the compartments 11 can be made from plastic profiles of square, rectangular or circular section. The use of transparent plastic material also allows a visualization of the reactive metal balls inside the reactor body 1. The modular assembly of the reactor body 1 makes it possible to give the reactor a high mechanical strength, avoiding the risks of deformation of the reactor body and consequently, to operate with much greater fluidized bed heights with a non-subdivided reactor body. With this type of assembly, it is possible to consider reactors of 3, 4 or 5m high, while with such materials, the maximum heights possible so far were of the order of 2m.

  The injection chamber 2 of the reactor of FIG. 1 is preferably cone-shaped (circular base section) or trapezoidal (rectangular base section), flared upwards. It contains, in addition, balls 12 made of material inert with respect to the solution, for example glass, plastic or alumina, intended to improve the fluidization of the solution and its homogeneity as soon as it enters the body. 1. The balls 12 of inert material filling the injection chamber 2 preferably have a particle size greater than the initial particle size of the reactive metal beads loaded into the reactor. The injection chamber is further constituted to reduce any turbulence caused by the fluid velocity. This can be achieved in particular by the flared shape of the injection chamber, which may comprise baffles (not shown) capable of breaking the flow and the speed of the liquid.

  The volume of the injection chamber 2 is calculated so as to reduce all the disturbing phenomena inherent to the injection and the flow of a liquid solution in any pipeline and / or any system operating in aqueous phase. The injection chamber 2 thus makes it possible to significantly improve the hydrodynamic parameters of the device.

  As shown in FIG. 1, a grid 13, in the form of a honeycomb, is preferably disposed between the reactor body 1 and the injection chamber 2. The solution thus passes from the injection chamber 2 to the reactor body 1 through the cells of this grid. This makes it possible to limit the turbulence during the injection of the solution into the reactor body 1, by breaking up the flow of liquid and by homogenizing the injection.

  A drain line 14, provided with a purge valve, is arranged laterally in the lower part of the injection chamber, to allow the balls 12 to be discharged from the injection chamber 2 as well as the entire bed. if necessary.

  The agitation device of the fluidized bed in the reactor body 1 is chosen in particular according to the type of reactive metal balls used in the reactor. It can especially use ultrasound and / or electromagnetic waves.

  As shown in FIG. 5, in which the possible subdivision of the reactor body 1 into compartments is not shown, the stirring device may be of ultrasonic type. It then preferably comprises a plurality of ultrasonic transducers 15, which may be of the same type as the sonotrode illustrated in FIG. 2 and each comprise from one to seven active heads. The ultrasonic transducers 15 are preferably distributed at the periphery of the reactor body, from top to bottom of the reactor body 1 and offset laterally with respect to one another in order to increase the kinetics of the chemical reactions all along the reactor. . These ultrasonic transducers may, for example, be placed every 20 to 100 cm, evenly and alternately depending on the symmetry of the reactor body 1.

  This type of stirring makes it possible to use amagnetic reagent metal beads, such as zinc, and to establish mixed beds with balls of different kinds, by weighting the size thereof according to their density.

  As shown in FIG. 6, in which the possible subdivision of the reactor body 1 into compartments is not shown either, the stirring device may be of the electromagnetic type. This type of stirring device is more particularly suitable for cementation reactors in which the active metal balls comprise iron. The stirring device then preferably comprises electromagnets 16 (FIG. 7), for example each constituted by a winding of copper wire around a soft iron core, arranged so as to surround the reactor body 1 with using a caloriport resin support, in which the electromagnets are inserted. In a preferred embodiment, the electromagnets 16 are mounted on a support block 17 constituting a movable carriage, which can be driven by an alternating vertical movement, symbolized by the arrow 18 in FIG. 6. The speed of movement of the block of support 17 may, for example, vary between 0 and 1 m / s. The mechanical system for reciprocating the support block 17, which can support an electromagnetic mass of up to 500 kg, is for example composed of two vertical isometric rails 19, a belt of reinforced polypropylene drive, aluminum pulleys having undergone surface hardening treatment and an asynchronous electric motor, preferably managed by an automaton (not shown).

  In a preferred embodiment, the support block 17 also supports demagnetizing electromagnets 20. These are preferably constituted by coils embedded in a heat transfer resin, which also surrounds the stirring electromagnets 16 for activation of the reaction. The demagnetizing electromagnets 20 are intended to eliminate, or at least to minimize, the remanent magnetization generated by the stirring electromagnets 16 on the ferromagnetic materials comprising all or part of the active bed. For this, the demagnetizing electromagnets 20 are connected in opposition of pole and phase and are less powerful than the stirring electromagnets 16, so as to act only on the remanent magnetization. This makes it possible to improve the different kinetics of the chemical reactions.

  For example, a cementation reactor having a reactor body 1 having a width of 1.2 m and a thickness of 10 cm has been produced, corresponding to a useful sector of the intermediate portion of the order of 1200 cm 2. The porosity at the base of the modules being of the order of 0.5 and the linear velocity of the order of 12 cm / s, such a reactor makes it possible to cement the cupric ions with a solution flow rate of 50 m 3 / h and a fluidized bed operating with iron balls with an average diameter of 2.5 mm.

  The injection chamber 2 of this cementation reactor has a rectangular base of 20 x 10 cm and widens upwards to reach the dimensions (10 x 120 cm) of the reactor body 1. It is 50 cm in height and is filled with balls 12 of inert material, for example alumina, plastic or glass, having a particle size of between 0.3 cm and 1 to 2 cm. The amount of balls 12 of inert material disposed in the injection chamber 2 is calculated so as to form a ball bed 12 very slightly expanded.

  The flared finishing compartment 6 of this reactor has a height of 80cm, a maximum section of 2.8m2. In the finishing compartment, much quieter, the linear velocity of the fluid is of the order of 5, 1cm / s. This part is activated using ultrasonic transducers. It makes it possible to stay much longer the fine iron particles entrained out of the fluidized bed whose diameter is between 0.8 and 0.5mm.

  The average porosity at the base of the finishing compartment 6 is close to 0.7 while it is greater than 0.9 at the discharge duct 4. The entrained particles have a diameter of approximately 0.4 mm. The flaring of the reactor in the finishing compartment 6 makes it possible to reduce the consumption of iron constituting the reactive metal from 80/90% to 95/98%.

  In this example, the stirring device consists of ultrasonic transducers 15 placed as shown in Figure 5. The sonotrodes bathed in the solution are made of titanium and the fasteners are made on vibration nodes. They can be activated by screwing the piezoelectric bodies on fixed bases (not shown).

  Furthermore, the modular assembly of the reactor body 1, subdivided into compartments 11, makes it possible to increase the height of the reactor and, consequently, to lower the final copper content of the solution by at least a factor of 2 .

  The following example makes it possible to compare the results obtained with the same reactor with and without finishing compartment 6. The reactor is used for the treatment of a sulfuric solution at pH 2 of copper sulphate at 4 g / l by carburizing on particles of iron. The reactor body 1 has a height of 3m, a width of 0.6m and a thickness of 0.1m. It is composed of 4 compartments 11 of 15cm wide.

  In the absence of a finishing compartment 6, the solution is evacuated through the discharge pipe with a flow rate of 25m3 / h and a content of 0.3g / l of copper, making it possible to produce 93kg of copper contained in 104kg of elements. , a recovery rate of 89%. Iron consumption is 102.1 kg, a yield of 80%. The trapped residual iron particles represent 11.5 kg and have a particle size of between 0.4 and 0.6 mm.

  By placing on the reactor body 1 a flared finish compartment 6, 80 cm high and 1.4 m 'maximum section, provided with three ultrasound emitting elements 7 of 1000 watts each, the solution discharged through the duct d evacuation 4 then comprises only 0.05 g / l of copper. The quantity of copper elements produced rose to 102.1 kg, a recovery rate of over 98% for a purity of up to 99%.

  It is thus possible, thanks to the presence of the finishing compartment 6, recovering 6.25kg of additional copper per hour, which corresponds, in continuous operation, to 50 tonnes / year for a limited additional energy expenditure.

  The device described above thus makes it possible to overcome the most important limitations relating to fluidized bed reactors. Indeed, these limitations are essentially related to the injection of the solution, the reactivity of the fine particles in the upper part of the fluidized bed and the mechanical strength of the walls of the reactor body, especially when they are plastic, and the reactor described above makes it possible to improve these various parameters.

Claims (11)

claims   1. Device for implementing liquid / solid reactions in a fluidized bed comprising a vertical reactor body (1), means (3) for injecting a solution to be treated at the lower end of the reactor, means ( 5) for introducing a reactive metal into the reactor, means (4) for evacuation at the top of the reactor and means for stirring the solution, characterized in that it comprises, at upper end of the reactor body (1), a flared finishing compartment (6) in which ultrasonic emitting elements (7) are immersed in the solution.   2. Device according to claim 1, characterized in that the reactor body (1) is subdivided into a plurality of parallel vertical compartments (11).   3. Device according to claim 2, characterized in that, the reactor body (1) being cylindrical, the compartments (11) have the form of concentric annular cylinders.   4. Device according to claim 2, characterized in that said vertical compartments (11) are separated by flat vertical walls.   5. Device according to any one of claims 1 to 4, characterized in that it comprises, at the lower end of the reactor body (1), a cone-shaped injection chamber (2) or trapeze, flared up.   6. Device according to claim 5, characterized in that balls (12) of inert material are arranged in the injection chamber (2).   7. Device according to claim 6, characterized in that said beads (12) are made of glass, plastic or alumina.   8. Device according to any one of claims 5 to 7, characterized in that it comprises a grid (13) in the form of a honeycomb between the reactor body (1) and the injection chamber (2) .   9. Device according to any one of claims 1 to 8, characterized in that the stirring means comprise ultrasonic transducers (15) distributed at the periphery of the reactor body (1).   10. Device according to any one of claims 1 to 8, characterized in that the stirring means comprise electromagnets (16) arranged around the reactor body (1) and drive means for printing the electromagnets a alternate vertical movement.   11. Device according to claim 10, characterized in that it comprises a block (17) for supporting the electromagnets (16) also comprising demagnetizing electromagnets (20) for eliminating the remanent magnetization of ferromagnetic particles constituting the reactive metal.